The present invention relates in general to a mudring which may be attached to a conventional electrical junction box, and in particular to adjustable mudring which may be attached to conventional electrical junction box to enable positioning the front of the mudring at selectable distance from the junction box. More specifically the present invention relates to a adjustable mudring used to enable the positioning of the front of the mudring flush with the surface of the wall regardless of the relative position of the junction box in relation to the wall.
Because of various state and federal codes, the wiring of a building requires the use of metal conduit for holding electrical wires, and so-called electrical junction boxes on which may be mounted a variety of electrical devices for access by the user of the building. Such junction boxes are mounted within the walls of the building, with openings provided in the walls for access to the junction boxes. These openings are usually smaller then the junction box itself. Mudring of a different size is attached to the junction box. The junction box remains concealed behind the sheathing of the wall (drywall, plaster). Replacement of the junction box or the mudring attached to the junction box is impossible without disturbing the wall finish and sheathing. The mudring has depth equal to the thickness of the sheathing and extends true the opening in the wall. It is desirable that the open front of the mudring is positioned adjacent to the surface of the wall so that when a switch or plug is mounted in the junction box, the front of the switch or plug will be substantially flush with the surface of the wall. Another reason of exact positioning of the junction box is that some state end local codes require minimum distance from the face of the mudring to the wall plate covering the outlet (switch). However because of the wide variety of types of walls in which the conduit and electrical junction boxes are installed, and because the junction boxes are typically installed before the wall surfaces are applied to studs or to like, it is difficult to estimate the proper location of the junction box to ensure that the front of the switch or plug will be flush with the wall surface. Sometimes the junction boxes are not installed at the right position according to the wall sheathing (at different angle) which is an additional problem for the proper installation of the outlet or switch. If the mudring protrudes out from the wall surface, then the switch or plug will appear unsightly, whereas if the junction box is recessed too far from the wall surface, than the switch or plug to be mounted therein may not be adequately protected from spark or other electrical hazards reaching surrounding combustible materials. In many cases when the junction box is installed to deep into the wall the switch or outlet does not have support on the surface of the wall and the switch or outlet is going to deep into the wall that the wall plate can not cover it or the screws connecting the switch (outlet) to the mudring have to be left loose and then a good ground between the switch or outlet and the junction box is missing. Furthermore, if the junction box is too far, recessed from the wall surface, it may, not even be possible to mount the switch or plug therein.
In many cases during the construction or after the construction is completed, the user of the building decides to change the finished surface of the wall by installing a ceramic tiles or paneling, or the user of the building is planing to have a paneling in the future but at this moment he wants to stay with plain walls. In this case an adequate for the present moment mudring is installed. In the future in order a new wall surface to be installed the already finished wall has to be cut for installation of a new, deeper mudring and the surface of the wall patched again.
A number of adjustable electrical outlet boxes have been proposed to allow mounting a switch or plug so that it is substantially flush with a wall surface. Among these are those disclosed in U.S. Pat. Nos. 707,247 1,975,101 2,048,611 3,433,886 5,289,934 5,098,046 5,114,105 5,253,831 and 4,634,015. Most of these arrangements show combination specialized junction box and slidable element for holding a switch or plug and as such require installation of the specialized junction box everywhere the device is to be used. That is, the device cannot be used with conventional junction boxes and so if the device is going to be used it must be installed at the beginning. This may result in an unnecessary expense since a conventional junction box might have been just as suitable, but such determination is often difficult before the building is constructed. Also, some of the disclosed arrangements allow for adjustment screws or other implements to protrude into the space occupied by electrical wiring which, of course, could be dangerous.
Other invention such as U.S. Pat. No. 4,634,015 partially solves these problems but it is vary difficult to manufacture the collar and the frame to fit exactly in slidable contact and to insure permanent ground. Because of corrosion between the two sliding surfaces the electrical contact is lost, This problem is solved with the present invention because the bolts used for adjustment are used at the same time for tightening the collar to the frame. By that the electrical contact is guaranteed at all times.
Another problem with U.S. Pat. No. 4,634,015 is that for adjusting the collar to the frame a very complicated construction is used It requires special bolts and washers. This construction makes that adjustable outlet box difficult for manufacturing and for assembling and more expensive. This problem doesn't exist with present invention because of shelf bolts are used and the construction of the collar and the frame permits easy manufacturing and wide allowance for assembly.
The proposed junction box in U.S. Pat. No. 4,634,015 is adjustable in some limits and the frame can not be replaced with deeper one after the construction of the wall is completed. The present adjustable mudring permits replacement of one frame with another at any time and by that covers unlimited distance of adjustment.
Another advantage is that this invention permits movement of the frame not only outward and inward but rotation around any axle parallel to the lip of the collar. By that the edge of the adjustable mudring can be adjusted perfectly parallel to the surface of the wall no matter how the junction box is installed.